1. Field of the Invention
This invention relates to driving systems and more particularly it concerns novel hydraulic hammers for driving piles and similar elements.
2. Description of the Prior Art
Hydraulically driven hammers are described in copending U.S. application Ser. No. 391,569 filed Aug. 27, 1973 and in U.S. Pats. Nos. 3,283,832, 3,298,447, 3,431,986. In each of these prior disclosures a piston, which is connected to or forms part of a ram, moves along inside a stationary cylinder. U.S. Pat. No. 3,298,447 also discloses a differential type actuating piston and cylinder assembly wherein a smaller diametrical, or working area region on one side of a piston is continuously supplied with hydraulic fluid at high pressure while the opposite side of the piston, which is of larger diametrical or working area is alternately switched between high and low pressure.
In U.S. Pat. No. 3,417,828 there is described a hydraulically driven hammer wherein a cylinder incorporated into a moveable ram is driven up and down along a stationary piston. This last mentioned patent, however, provides no disclosure of differential hydraulic driving. A similar arrangement, using steam, is disclosed in U.S. Pat. No. 1,158,839.